Generally, a compressor may be classified into a rotary type compressor and a reciprocating type compressor according to a refrigerant compression method. In the rotary type compressor, a volume of a compression space is varied as a piston performs a rotary motion or an orbiting motion in a cylinder. On the other hand, in the reciprocating type compressor, a volume of a compression space is varied as a piston performs a reciprocating motion in a cylinder. As the rotary compressor, a rotary compressor for compressing a refrigerant as a piston is rotated by using a rotational force of a motor part is well-known.
The rotary compressor is configured to compress a refrigerant using a rolling piston which executes an eccentric rotary motion at a compression space of a cylinder, and a vane for dividing the compression space of the cylinder into a suction chamber and a discharge chamber by contacting an outer circumferential surface of the rolling piston.
Such a rotary compressor may be classified into a single rotary compressor and a double rotary compressor according to the number of compression spaces. The double rotary compressor may include a type for forming a plurality of compression spaces by laminating cylinders each having a single compression space on each other, and a type for forming a plurality of compression spaces at a single cylinder. In the former case, a plurality of eccentric portions are formed at a rotational shaft with height differences, and are configured to alternately compress a refrigerant at two compression spaces and to discharge the compressed refrigerant, while the eccentric portions perform an eccentric rotary motion at the compression space of each cylinder. On the contrary, in the latter case, as shown in FIG. 1, a refrigerant is simultaneously compressed at two compression spaces V1 and V2 and then is discharged, while a roller performs a concentric rotary motion at a single cylinder 3 provided with an oval-shaped roller 2 at a rotational shaft 1. In the latter case, since the refrigerant is sucked, compressed and discharged in the two compression spaces V1 and V2 with the same phase, gas forces transmitted to a central region of the rotational shaft 1 are attenuated. As a result, a repulsive force in a radial direction may almost disappear, and vibration noise of the compressor may be reduced.
However, the conventional rotary compressor having the oval-shaped roller may have the following problems.
As the roller 2 rotates together with the rotational shaft 1, an outer circumferential surface of wing portions 2a, 2b formed at two sides of the roller 2 consecutively contacts an inner circumferential surface (3a) of the cylinder 3. In this case, since contact ends 2a1, 2b1 of the wing portions 2a, 2b come in point-contact with the inner circumferential surface (3a) of the cylinder 3, an oil film may not be smoothly formed and a frictional loss may be increased.